Recently, there has come to be known a new class of road vehicle, namely, the three wheeled road vehicle having two wheels in the front and one wheel in the rear. Because of its novelty, there is as of yet no generic name for this class of vehicle. One example of a vehicle of this type may be found in U.S. Pat. No. 6,948,581 assigned to Bombardier Recreational Products Inc. (BRP Inc.), the assignee of the present application. A commercial example of such a vehicle is the CAN-AM™ SPYDER™ vehicle sold by BRP Inc., details of which may be found at the internet web address: spyder.brp.com/en-US/.
As would be recognized by one skilled in the art, and as has been described in some of the patent documents incorporated by reference into this application, the stability of these three wheel road vehicles is inherently less than that of four wheel automobiles. Although the stability of such three wheel vehicles is both safe and adequate for the vehicles' intended purpose, i.e. road use, it is nonetheless desirable for manufacturers of such vehicles to further control their stability as much as possible. This is true particularly in view of the fact that these vehicles are new on the market and operating them is somewhat different than operating an automobile or a motorcycle, vehicles with which riders will be more familiar.
One means for increasing a vehicle's stability is through the use of an Electronic Stability System (ESS). In basic terms an ESS uses an on-board computer processor and associated memory that have programming to manage various vehicle systems (e.g. engine, braking, steering, etc.) to a degree to which the human operator of the vehicle cannot. ESS's for four-wheel automotive vehicles and the benefits thereof have been known for some time. Given their benefits, such systems are now found, in one form or another, on many automobiles currently on the market.
In view of the desirability of enhancing the stability of a three wheel vehicle and in view of the benefits of an ESS on a four-wheeler, one of the first attempts (if not the first attempt) was made to incorporate a then existing ESS for an automobile into such a three wheel vehicle. As a result of that attempt, as is described in U.S. Patent Publication No. 2006/0180372 (incorporated by reference hereinabove), it was realized that the lack of a fourth wheel and the geometry of the vehicle (and particularly the geometry of the remaining wheels) prohibited the direct usage of such an automotive ESS system on a three wheeled vehicle. Modifications (also as described in that patent publication) were necessary.
While the system described in the '372 publication functioned as intended, it was merely a first attempt. The efforts described in the '372 publication were mainly focused on modifying the then existing automotive ESS to cause it to simulate its behaviour on a four-wheel vehicle. In words, the inventors of those inventions focused their attention making the three wheel ESS perform (to the extent possible) as if it were a four-wheel ESS.
After experimentation with a vehicle equipped with the system described in the '372 publication and theoretical calculations, the present inventors realized that while the first generation system adapted an ESS to a three wheel vehicle to overcome the disadvantages of a three wheel vehicle with respect to an ESS and four wheel vehicles, it did not take into account all of the characteristics of a three wheeled vehicle. Specifically, while it was known that it was easier to roll three wheel vehicles over, previous efforts were not focused on why this was the case, they were simply focused on stabilizing the vehicle when a situation indicative of an imminent rollovered occurred.
Therefore, while the first generation ESS for three wheeled vehicles was adequate for its intended purpose, improvement was still possible and further enhancing the stability of the vehicle was desirable.